The invention relates to a vehicle having an internal combustion engine to which a control unit and a starter are assigned, which starter draws electric power from the vehicle's electrical system battery to start the internal combustion engine.
Modern vehicles have a multiplicity of electric power consumers or loads. Ensuring a high availability of power to these consumers requires complex power management of the onboard electrical power system. Two-battery vehicle electrical systems, in particular, guarantee high energy availability; see, for example DE 102 29 018 A1.
High energy availability is particularly important in order to ensure a successful start of the vehicle. In the event of a vehicle start failure, i.e. in the event of an unsuccessful attempt to start the internal combustion engine, the vehicle must be tow-started or jump-started in order to start the engine. A jump-start design for a vehicle that has a two-battery vehicle electrical system is described, for example, in DE 103 61 743 A1.
One object of the invention is to provide an improved vehicle.
This and other objects are achieved according to the invention by a vehicle having an internal combustion engine, to which a control unit and a starter are assigned. The starter draws power from an electrical system battery of the vehicle in order to start the internal combustion engine. A backup battery can be connected in parallel to the electrical system battery, with an electrical connection element being located between the electrical system battery and the backup battery. This connection element can be controlled by the control unit with respect to the establishment of a conductive electrical connection between the backup battery and the electrical system battery. In the event of a failed engine start, the connection element will connect the backup battery to the electrical system battery in order to effect a recharging of the electrical system battery with a predetermined quantity of electric energy from the backup battery.
This means that the control unit can initiate a transfer of energy from the backup battery to the electrical system battery following an unsuccessful attempt by the user to start the vehicle. The predetermined amount of energy to be transferred is calculated such that the amount of energy is sufficient to successfully start the engine under normal conditions.
According to a preferred aspect of the invention, the vehicle includes a central operating unit and/or an instrument cluster, on which the recharging process can be indicated during recharging in the form of a visual display.
According to this variant, following the start failure and during the recharging process, a visual indication that recharging is underway is displayed to the user of the vehicle. Once recharging is complete, the visual display is terminated, or the visual display indicates readiness for an engine start.
Thus, the user receives visual notification of the readiness of the vehicle for a new attempt to start the engine once recharging is complete. This offers the advantage that, following an unsuccessful start attempt, the user can be afforded at least one additional promising start attempt, and the user is prepared for such a start attempt by being notified of measures taking place in the vehicle to enable the additional start attempt.
According to a preferred embodiment of the invention, the display includes a timer, with the timer indicating, at the time of recharging, the estimated amount of time remaining until recharging is complete. Thus, the user is notified as to the amount of time remaining for measures being implemented in the vehicle to afford the user the additional attempt to start the vehicle.
According to a particularly preferred aspect of the invention, the connection element is designed as a switch, and a battery sensor that determines the amount of recharging current flowing during the recharging process is assigned to the electrical system battery.
According to another embodiment, the connection element is designed as a d.c. chopper circuit, and a battery sensor is optionally assigned to the electrical system battery, with the d.c. chopper circuit or the battery sensor determining the amount of recharging current flowing during the recharging process.
The use of a d.c. chopper is particularly advantageous. The d.c. chopper determines the voltage being applied to the power interface assigned to the electrical system battery, i.e. essentially the voltage at the electrical system battery. If said voltage drops below a predetermined threshold value following initialization of the d.c. chopper, this can be used as an additional criterion for initiating the recharging process. In this case, an unsuccessful engine start is not a required precondition. If, in contrast, the voltage does not drop below a predefined threshold value following initialization of the d.c. chopper, the control unit can implement a transfer of energy from the backup battery to the electrical system battery via the d.c. chopper after an unsuccessful start attempt has been carried out by the vehicle user.
Information about the recharging current, e.g. obtained by measurement using a battery sensor which measures the battery voltage and the battery power, is necessary for the timer to determine the duration.
For this purpose, the control unit, the d.c. chopper or the battery sensor predicts, according to the principle of extrapolation, the amount of time remaining until the amount of energy transferred reaches the predetermined amount of energy, based on the determined recharging current.
In this process, a one-time determination of the recharging current at the start of recharging is carried out and, assuming a constant recharging current, the amount of time remaining until the predetermined amount of energy is reached is predicted. Alternatively, the recharging current is measured repeatedly during the recharging process and the amount of energy actually transferred is determined by time integration; then, on the basis of this variable, applying the principle of linear extrapolation, the amount of time remaining until the predetermined amount of energy is reached is predicted.
The invention is based on the following considerations.
Conventional vehicles today have a 12-volt energy store (for example, a battery). If the charge status of the energy store is below the startup limit, there is a risk of breakdown. In vehicles that have a two-battery electrical system, a recharging function can be used to prevent breakdowns. With such a function, with the help of a DC/DC converter and a second battery, the level of charge that is required for a start can be fed back into the main battery. This can be made apparent to the user of the vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawing.